Self-regulating reciprocating pumps



A ril 17, 1962 P. E. BESSIERE 3,029,737

SELF'TREGULATING RECIPROCATING PUMPS Filed Jan. 8, 1959 I 26 25 V M A :45 go 28 INVENTOR Berra ffl'elm B an-avg."

3,029,737 SELF-REGULATING RECIPROCATING PUMPS Pierre Etienne Bessiere,55 Blvd. du Commandant Charcot, Neuilly-sur-Seine, France Filed Jan. 8,1959, Ser. No. 785,738 Claims priority, application France Jan. 21, 19584 Claims. (Cl. 103-4) The present invention relates to reciprocatingpumps which are automatically regulated as a function of the speed byvariation of the feed of liquid to the pump. This invention is moreespecially but not exclusively concerned with fuel injection pumps forinternal combustion engines, and in particular diesel engines.

In known pumps of this kind, the beginning of liquid delivery (forinstance to fuel injectors) is more and more delayed as the deliveryflow rate decreases. In the case of a fuel injection pump for aninternal combustion engine, where the factor of regulation is the numberof revolutions per unit of time, the advance to injection is thereforereduced when the engine is running on low loads.

The object of the present invention is to provide a self-regulating pumpof the above mentioned kind which is better adapted to meet therequirements of practice than those known at the present time and inparticular which is such that the beginning of effective delivery isindependent of the amount of liquid supplied on every delivery stroke.

The invention consists chiefly in causing every delivery stroke of afirst piston driven at a speed proportional to the speed whichconstitutes the factor'of regulation to produce through hydraulic meansa delivery stroke of a second piston (or shuttle) which delivers liquidfrom a pump chamber from which starts a delivery eonduit and into whichopens a feed conduit, means being provided to achieve a hydraulictransmission of the movements of the first piston to the second pistonas soon as the first piston starts on its delivery stroke and to producethe return stroke of the second piston, or shuttle, under the effect ofthe pressure under which liquid to be delivered by the pump is fed tothe pump chamber, means being further provided for delaying thebeginning of the feed of liquid to said pump chamber until after thebeginning of the return stroke of the first piston and/or for brakingthe flow of the liquid through United States Patent the feed conduit tothe pump chamber and/or for braking the return stroke of the secondpiston or shuttle.

A preferred embodiment of the present invention will be hereinafterdescribed with reference to the accompanying drawing, given merely byway of example and in which the only FIGURE diagrammatically shows inaxial section a fuel injection pump made according to the invention.

The pump includes a first piston 1, the delivery strokes of which arehydraulically transmitted to a second piston 2 which constitutes thepump piston proper. Piston 1 is reciprocated in its cylinder 3 by meansof a cam 4 at a rate proportional to the speed of the internal com-'bustion engine which is to be fed with fuel from the pump, said speedconstituting the factor of regulation. in the usual manner, the campositively drives piston 1 during its delivery stroke, whereas a spring5 drives said piston during its return stroke. A liquid feed conduit 6opens into cylinder 3 at a point such that the opening of this conduitinto this cylinder is cleared only when piston 1 is in its lower deadcenter position (as shown by the drawing), this opening being closed assoon as piston 1 starts on its delivery stroke (upward stroke). Theliquid fed through feed conduit 6 to cylinder 3 is a liquid capable ofensuring the hydraulic transmission from piston 1 to piston 2. Thisliquid may,

2 at least in some cases, be the fuel that is to be delivered by thepump.

Piston 2 reciprocate-s in a pump cylinder 3 and forms with the upperportion of this cylinder the pump chamber proper. A feed conduit 8 opensinto this pump chamber to supply it with the fuel to be delivered by thepump. A delivery conduit 9 advantageously provided with a check-valve 10leads out from said pump chamber. The lower portion of cylinder 7 andthe top portion of cylinder 3 are constantly in communication with eachother, for instance through an opening 11 provided in partitionextending between these two cylinders. This partition serves to supportthe lower end of a relatively weak spring 12 which urges piston 2 in thedirection of its delivery stroke. Cylinder 7 is further provided with adischarge conduit 13 which is cleared by the bottom edge of piston 2when said piston, during the delivery stroke of piston 1, reaches theend of its own delivery stroke under the effect of the hydraulictransmission existing between pistons 1 and 2. As soon as piston 2clears conduit 13, its delivery stroke is stopped. Of course, means,which will be more explicitely referred to hereinafter, are provided forclosing feed conduit 8 during the delivery stroke of piston 2 so thatthe fuel present in the pump chamber of cylinder 7 can be deliveredduring said delivery stroke through conduit9 toward the injector orinjectors to be fed with fuel.

According to one of the characteristic features of the invention, thereturn (downward) stroke of piston 2 (which stroke takes place duringthe return stroke of piston 1 and/or during the period for which saidpiston 1 is in its lower dead center position and clears the opening ofconduit 6) is produced by the pressure of the fuel fed through conduit 8into the pump chamber of cylinder 7 above piston 2.

This pressure must therefore be higher than that of the liquid fedthrough conduit 6 and, as a matter of fact, it must be higher than thesum of this pressure and of the force exerted by spring 12 upon piston2, if such a spring exists. Actually, spring 12 might be replaced by themere effect of the friction of piston 2 against the inner wall ofcylinder 7.

Furthermore, according to another characteristic feature oftheinvention, feed conduit 6 is made to supply a 'sufiicient amount ofliquid into cylinder 3 to completely fill up the space existing betweenpistons 1 and 2 when piston 1 starts on its upward stroke. Finally, andalso according to a characteristic feature of the invention, means areprovided for delaying the beginning of the feed or for braking the feedin conduit 8 or for slowing down the return movement of piston 2, thusto produce a reduction of the useful stroke of said piston 2.

In the embodiment of my invention illustrated by the drawing, I makeuse-of means which are particularly efficient and work with a highaccuracy for causing the beginning of the return stroke of piston 2 totake place with a lag with respect to the beginning of the return strokeof piston 1. These means include a slide valve 14 inserted in feedconduit 8 and controlled in such manner that it closes said conduitduring the delivery stroke of piston 1, but opens said conduit 8 with agiven lag with respect to the beginning of the return stroke of piston1, this lag being preferably adjustable.

For this purpose, slide evalve 14 is slidably mounted in a cylinder 15and it is subjected to the action of a spring 16 tending to apply slidevalve 14 against a shoulder 17. When slide valve 14 is in contact withthis shoulder, its groove 18 opens the flow through conduit 8.Furthermore, the lower end of cylinder 15 is connected through a conduit19 with a conduit 21, itself connected, with the interposition of acheck-valve 20, with a cylinder 22 in which is slidably mounted a piston23 rigid with piston 1. In the arrangement shown by the drawing, returnspring 5 is housed in cylinder 22 and one of its ends bears againstpiston 23 whereas the other end bears against the pump body. A feedconduit 24 opening mto cylinder 22 has its outlet cleared by piston 23when said piston is in its lower dead center position (as shown by thedrawing) so that cylinder 22 can then be filled w th liquid. This liquidmay be the same as that fed to cylinder 3 through conduit 6, so thatconduits 24 and 6 may branch out from a single feed conduit 25. Theportion of conduit 21 extending downstream of check-valve and of thepoint where conduit 19 branches otf therefrom includes a throttledportion 26 preferably adjustable by means of a screw valve 27. Thisportion of conduit 21 further includes a valve member 28, for instanceof the form of a grooved slide valve adapted to close conduit 21 as longas piston 23 is moving on its upward stroke. For this purpose, slidevalve 28 is actuated in such manner as to close conduit 21 under theeffect of the pressure existing in cylinder 22 during the upward strokeof piston 23, this pressure being transmitted through a conduit 29 tothe cylinder 30 in which slide valve 28 is slidable. Slide valve 28 isreturned into the position where it opens conduit 21 (as shown by thedrawing) by a spring 31.

Consequently, when piston 23 is moving on its upward stroke, it causesthe simultaneous closing of conduits 8 and 21. The upward movement ofslide-valve 14 stops when the lower edge thereof clears a notch 32provided in the portion 8a of conduit '8 located upstream of said slidevalve 14. This notch 32 permits the excess of liquid delivered by piston23 to escape to the outside without causing conduit 8 to be opened. Theclearing of notch 32 by slide valve '14 determines the upper limitposition of said slide valve. In this position, the lower edge of groove18 is located at a distance above the top of conduit 8. Slide valve 14remains inisaid upper position until pistons 1 and 23 start on theirdownward strokes. Then, slide valve 28 is pushed upwardly by spring 30and clears conduit 21 so that slide valve 14 can start movingdownwardly. However, in view of the fact that the lower edge of groove18 is at some distance above conduit 8, the opening of said conduit doesnot take place immediately as pistons 1 and 23 start moving down. Sometime elapses before conduit 8 is being opened, this delay being due tothe braking of the liquid driven out through conduit 21 by slide valve14 as it flows past the throttled passage 26 (check-valve 20 preventingany return of the liquid toward cylinder 22). I thus obtain a lag of thebeginning of the feed of fuel to cylinder 7, with respect to thebeginning of the return stroke of piston 1. This lag may be adjusted byvarying the cross sectional area of throttled passage 26 and/or varyingthe compression of spring 16 (through means not shown on the drawing).

The operation of the lows:

Since, at the beginning of the upward stroke of piston 1, the wholespace between said piston and piston 2 is pump abovedescribed is asfolfilled with liquid, the delivery stroke of piston 2 starts just whenpiston 1 closes the opening of feed conduit 6. This delivery strokelasts until the lower edge of piston 2 clears the opening of dischargeconduit 13. Spring 12, if such a spring has been provided, is too weakto cause the upward stroke of piston 2 to go on after this time. Duringthis delivery stroke, slide valve 14 keeps feed conduit 8 closed so thatthe liquid present in the upper chamber (pump chamber) of cylinder 7delivers fuel into conduit 9, during said upward stroke of piston 2.

When piston 1 starts on its return stroke (downward stroke), slide valve14 is still keeping feed conduit 8 closed so that piston 2 remains inits upper position where it is kept by spring 12 or merely by thefriction against the wall of cylinder 7. It is only when slide valve 14,during its braked downward movement, opens feed conduit 8 75 feedconduit 8 to that the fuel under pressure supplied to cylinder 7 pushespiston 2 downwardly so as to fill up the pump chamber of cylinder 7.

As long as the speed at which piston 1 is driven is below a given value,the fuel fed through conduit 8 is given suflicient time, despite the lagin the opening of this conduit, to push back cylinder 2 to the maximumdistance determined either by the compression of spring 12 or by anabutment, before piston 1 starts on its next upward stroke which isimmediately transmitted to piston 2. Consequently the amount of fuelsupplied on every delivery stroke of piston 2 into conduit 9 is maximum.If, on the contrary, the speed at which piston 1 is driven rises, due toan acceleration of the engine above said given value, piston 1 starts onits delivery stroke before the fuel arriving through feed conduit 8 hasbeen given time to push back piston 2 to the maximum distance. Thereturn strokes of this piston will then be the shorter as the speed ofpiston 1 .rises more and more above said given value. In other words,the volume of fuel that enters the pump chamber is the smaller as thespeed of piston 1 is higher in view of the fact that this volume isproportional to the time elapsing between the opening of conduit 8 byslide valve 14 and the beginning of the next delivery stroke of piston2, which coincides with the beginning of the delivery stroke ofpiston 1. I therefore obtain self-regulation without modification of therelative time at which injection begins because whatever be the positionof piston 2 in cylinder 7 when piston 1 starts on its upward stroke,piston 2 is immediately driven in the upward direction since, as abovestated, the interval between pistons 1 and 2 is wholly filled withliquid when piston 1 starts 3n its upward stroke and closes the openingof feed conuit 6.

If, for instance, when the speed is equal to the given value for whichself-regulation star-ts being obtained, the time for which feed conduit8 is opened is ,4 of the time elapsing between the beginning of thereturn stroke of piston 1 and the beginning of its next upward stroke,an increase of the speed of 10% is suificient to stop the. feed of fuelby the pump.

The fineness of regulation of the pump might be fur-- ther improved byhaving screw 27, which adjusts the cross sectional area of throttledpassage 26, controlled by a speed governor so that said cross sectionalarea is automatically reduced when the speed increases.

An analogous effect might be obtained, according to a firstmodification, by replacing the lag in the opening of slide valve 14 withrespect to the beginning of the return movement of piston 1 by a brakingaction exerter for instance by a throttled passage provided in feed conduit 8, the cross sectional area of said passage being either fixed orvariable as a function of the speed. This throttled passage would brakethe inflow of fuel through cylinder 7.

According to another modification, the speed of the return stroke ofpiston in the lower chamber of cylinder 7 a duit provided with able as afunction I might brake 2 by providing discharge cona throttled passagepreferably adjustof the speed, by inserting in this discharge conduit avalve member which closes it when piston 1 is moving upwardly and byinserting in the communication hole 11 provided between cylinders 3 and7 a check-valve permitting the flow of liquid only from cylinder 3toward cylinder 7.

Of course, in this last mentioned modification, the inside of cylinder3must be filled with liquid, fiowing through conduit 6, when pistonstroke so that this liquid, together with that present in the lowerchamber of cylinder 7, serves to transmit immediately the upwardmovement of piston 1 to piston 2.

In a general manner, while I have, in the above description, disclosedwhat I deem to be a practical and efficient embodiment of my invention,it should be well 1 starts on its upward understood that I do not wishto be limited thereto as there might be-changes made in the arrangement,disposition and form of the parts without departing from the principleof the present invention as comprehended within the scope of theaccompanying claims.

What I claim is:

l. A reciprocatinglaction pump which comprises, in combination, acylinder, a piston fitting slidably in said cylinder so as to formtherewith a pump chamber, a second cylinder fixed with respect to saidfirst mentioned cylinder, constantly open fluid communication meansbetween said two cylinders for connecting one end of said secondcylinder with said pump chamber, a piston fitting slidably in saidsecond mentioned cylinder so as to form therewith a pump chamber on theother side of said second mentioned piston from said end of said secondmentioned cylinder, means in communication with said first cylinder forfilling with liquid, from the beginning of every delivery stroke of saidfirst mentioned piston, the whole volume of said first mentioned pumpchamber, said communication means and the portion of said secondcylinder on the same side of said second piston as said end of saidsecond cylinder, means for reciprocating said first piston at a rateproportional to a factor of regulation, whereby every delivery stroke ofsaid first piston produces a simultaneous delivery stroke of said secondpiston, a delivery conduit leading out of said second pump chamber, afeed conduit opening into said second pump chamber for feeding liquid,under pressure thereto to produce the return strokes of said secondpiston, means, interposed between said second piston and said secondcylinder, for yieldingly opposing the return strokes of said secondpiston, said second pump chamber being filled with said liquid at theend of each of said return strokes and means operatively connected withsaid first piston for preventing the flow of liquid through said feedconduit to said second pump chamber until after the beginning of everyreturn stroke of said first piston.

. slidably in said second mentioned cylinder so as to form therewith apump chamber on the other side of said second mentioned piston from saidend of said second mentioned cylinder, means in communication with saidfirst cylinder for filling with liquid, from the beginning of everydelivery stroke of said first mentioned piston, the

whole volume of said first mentioned pump chamber, said communicationmeans and the portion of said second cylinder on the same side ofsaid'second piston as said end of said second cylinder,'means forreciprocating said first piston at a rate proportional to a factor ofregulation, whereby every delivery stroke of said first piston producesa simultaneous delivery stroke of said second piston, a delivery conduitleading out of said second pump chamber, a feed conduit opening intosaid second pump chamber for feeding liquid under pressure thereto toproduce the return strokes of said second piston, means, interposedbetween said second pistonand said second cylinder, for yieldinglyopposing the return strokes of said second piston, said second pumpchamber being filled with said liquid at the end of each of said returnstrokes, a slide valve inserted in said feed conduit for controlling theflow of said last mentioned liquid toward said second pump chamber, andmeans operatively connected with said first piston for closing saidslide valve during every delivery stroke of said first piston andopening it after the beginning of the return stroke of said secondpiston.

4. A pump according to claim 3' in which said means for closing saidslide valve are hydraulic means and said means for opening said slidevalve are resilient means, further including hydraulic means for brakingsaid open ing of said slide,valve.

References Cited in the file of this patent FOREIGN PATENTS 127,951Great Britain June 5, 191 9 402,603 Great Britain Dec.7, 1933

